Unconscious Lie Detection

Can people detect liars better if they just rely on their unconscious? What is the evidence for using gut feelings? There is little to no evidence that the unconscious can help us detect lies.

In our review (Street & Vadillo, 2016), we argue that research on unconscious lie detection does not exclude the possibility that conscious processes are being used to detect deception, and that methods thought to engage unconscious lie detection do not give accuracy rates any better than using methods that allow for conscious judgments. We have also recently commented on a recent unconscious lie detection theory called the ‘tipping point’, which we argue is untestable and contradicts itself (Street & Vadillo, 2017). Much of the research on unconscious lie detection uses the indirect lie detection method, described below. We show that this method does not allow us to claim anything about the unconscious – instead, it seems that indirect lie detection tells us about conscious judgments.

The “indirect lie detection” method is the largest body of research suggesting there are benefits to relying on the unconscious. To supposedly access unconscious thinking, participants are asked to judge only a single behaviour related to lying – is this person thinking hard or not? Liars generally end up in the thinking-hard category and truth-tellers in the not-thinking-hard category. In fact, this method better separates liars and truth-tellers than asking people to explicitly decide who is lying and who is not.

Lie-truth judgments include lots of clues, such as whether the person is thinking hard or not, telling a plausible story, and so on (left). This can cause confusion: thinking hard suggests lying, but a plausible tale suggests honesty. By focusing on only a single, reliable clue to deception, as the indirect lie detection method does (right), the potential for conflict is removed

The boost in accuracy has nothing to do with an unconscious store of additional knowledge. Instead, the benefit comes from using a single, reliable clue to deception – thinking hard – ignoring all the other behaviours present. But when people make lie and truth judgments, they also incorporate other behaviours, some of which the liar use to make themselves appear honest – e.g., telling a plausible tale. This creates a conflict: one behaviour suggests deception but the other suggests honesty. This gives rise to an ambiguity and increases the room for error in making the judgment. Reducing the conflict between cues by focusing attention to only a single reliable cue is what is thought to increase accuracy, which we call the focal account (Street & Richardson, 2015)

To spot a liar, we should not trust our intuitions. Instead, we should make reasoned, conscious judgments. Look for highly reliable clues like Pinocchio’s nose, and ignore those that have low reliability because they will increase the possibility of error.